a. Field of Invention
This invention pertains to a magnetically activated flashlight, and more particularly to a flashlight which is selectively activated by opening or closing a reed switch.
b. Description of the Prior Art
Typically flashlights, and more particularly handheld flashlights, include a generally cylindrical housing which contain one or more energy storage devices such as batteries. The cylindrical housing is terminated at one end by a transparent lens behind which there is provided an incandescent light bulb. Frequently the light bulb is surrounded by or otherwise provided with a reflector which collects light generated by the bulb and projects it outwardly through the lens. The shape of the reflector and the relative position of the reflector and bulb determines the geometric configuration of the light beam emerging from the flashlight. The beam may further be shaped optically by the lens.
One common problem for flashlights have been the switching means used for the selective activation and deactivation of the bulb. Most flashlights are provided with a strictly mechanical switch which consists of a pair of flexible blades disposed in parallel and separated by a preset distance. These blades are typically mounted inside the housing, between the housing wall and the batteries, about midway along the length of the housing. A sliding member is mounted on the outside of the housing and is mechanically interlocked with at least one of the blades. The member is slidably mounted on the housing and is arranged so that its movement along the housing selectively forces one of the blades to contact the other blade thereby establishing electrical contact therewith. This type of arrangement has not been reliable for a number of reasons. First, after repeated use, metal fatigue could cause the blades to be distorted easily so that they are either in constant contact or constant separation, independently of the action of the sliding member. Second, oxidation of the blades caused either by ambient atmosphere, or, more frequently, by gases vented from the batteries prevents the formation of a proper, that is, a low ohmic electrical contact between the blades even if the blades are in mechanical contact. A high ohmic contact between the blades results in a low level or even no light from the bulb. Third, because of the mechanical interconnection between the blades and sliding member, it is very difficult and expensive to make the flashlight waterproof. Fourth, because the blades have to fit between the inner housing wall and the batteries, the housing itself must be oversized. Thus, a larger, and more expensive housing is required. A fifth disadvantage of the above described arrangement is that arcing is produced between the blades which reduces the life of the light bulb, and causes pitting in the blades further degrading them.
There have been some attempts at solving some of these problems, for example by replacing the two blades requiring a physical force for electrical contact by a reed switch which uses a magnetic field for the same purpose. One such attempt is found in U.S. Pat. No. 3,792,389 to Murphy. However, in Murphy, the reed switch is made in a cavity formed in the housing thus sacrificing the housing integrity. In U.S. Pat. No. 4,152,755 to Trosper et al. a reed switch is provided inside the housing. However, in this arrangement a special axial space is required between the battery and the bulb to make room for the switch, thus requiring a longer and more expensive housing.
Independently of flashlights, in U.S. Pat. No. 3,151,263, to Jolly, a combination lamp and indicator is described which indicator is resettable by an external magnet.